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1998 Deville base
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Discussion Starter #1
Ive had an overheating scenario for a while. Theres no visible leaks. I did a CO2 coolant test 4 times and its not the head gasket. The first thing i replaced after it overheated was the thermostat. Then the radiator in case of a blockage. My crossover pipe is clear. Should i condemn the water pump or is there something else to try
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Please define "overheating".

Depending on conditions and vehicle climate control settings the engine temperature can normally vary from 190 to 225 degrees.

Water pump drive system in good condition ?
 

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1998 Deville base
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Discussion Starter #4
It gets ip past 250, tells me to idle it, then shut it off. It happened today after cresting a large hill on the highway. It happened on that same hill going the other direction about a month ago. A few minor hiccups since the first incident. I replaced the belt already and the tensioner was fine when i did it. The fans work. At least when they are commanded by the a/c

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And ive heard these thing can have the wp vanes eaten up by the dex cool if it gets too old. My grampa never flushed it in the 15 years he owned it. I did a flush at about 120k its got about 147k on it now

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Maybe i should re-do the co2 tests? Before today i thought i had it fixed and i was just being paranoid. This car is my baby and probably means more to me than the lives of my 3 yipping min-pins.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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You need to perform a cylinder block exhaust gas test. Rent the tester, buy the fluid, from any large parts store.

DEX-COOL does not, of itself, eat up cooling systems - neglected systems and old, rotten coolant eats up stuff.
 

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White Diamond '03 DHS (with DTS floor shift)
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forget the WP. Over heating on a hill climb is an early HG failure symptom.
Do the block test again right after an over heat episode.
 

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1998 El Dorado
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I am in the same boat with my 1998 el dorado- 70 k miles on florida car never driven over 75 mph ! It boils over after 15 minutes of highway. Block test passed 4 times by 2 different mecahnics. Cylinder pressures all equal at 148psi with one full crank. New radiator, wp, removed thermostat, cleaned surge tank, new surge tank cap, new coolant temp sending unit, purge lines clear, reverse flushed entire system when cold with garden hose and no blockages, heater core clear with good heat, fans work, new belt tensioner for wp, no leaks, runs fine. It all boils out the surge tank over flow at about 210 degrees ( used my own thermometer) before any warning lights come on or car overheats. I am going to pull the engine and do the head gaskets but before I do, is there anything that i am, missing ? thanks

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BTW - I did the bl;ock test while the car was steaming and boiling with tons of vapor - completely negative. Mechaninc did same !. Thanks
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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If the thermostat is still out, that's probably your problem right there. The correct one begins at 188 and is fully open at 206. If any steam or liquid entered the test tube then that test is faulty - wash the rig with fresh water and start over. Sample air-over-coolant only.

If the coolant you're testing is mostly water, of course it boils over at 210 with no pressure cap. If it boils with a pressure cap installed, then the system is not pressurizing to the proper 16 - 18 psi and it WILL boil over somewhere between 212 and 225 degrees.

Poor car has never been run ?? 75 mph is idling for a Northstar, especially the VIN Y version with the economy 3.11 ratio. 75 mph is only about 2100 rpm.

Go back through the sticky posts on this forum's main threads page - the ones on cooling systems, fan operation, and gauge operation. Maybe you're overlooking something.
 

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1998 Deville base
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Discussion Starter #9
Whats the difference between the coolant test an the block test? Ive heard its a hard test to do
 

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A coolant test determines the level of additives and lubricants still left in the coolant. Lab work.

A cylinder block exhaust gas test takes 30 seconds and is a piece of cake. Rent the tester, buy the fluid, from any large parts store and follow the directions - don't try to "make it better" by excessive bubble times. If you get raw coolant into the tester tube and cone it needs to be completely washed in fresh water and done again. You're testing the airspace over the coolant in the surge tank for the presence of exhaust gas hydrocarbons - gasket leaks.

Google "cadillac forums northstar exhaust gas test" or something close. Videos in Tech Tips.
 

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1998 Deville base
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Discussion Starter #11
Oh. I already did that. 4 times. Thats the CO2 test i referred to. I did it at work with the shop tester and fluid, twice using the engine vacuum method and twice using our hand vacuum pump. The first time drew up coolant and gave me a false positive. I washed it out and did it 3 more times to make sure. I wouldve done it more but my boss came out and i didnt want him to see me use all his fluid lol
 

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CO - Carbon monoxide, not 'dioxide'. If the tests were negative then you have some cooling system diagnosis to do.

In heavy or slow traffic with no A/C function set it's perfectly normal for these engines to warm to 224, fans go to SLOW, the engine cools to 213, the cycle repeats until you get back to open road and a bit of time at over 20 mph.

The 250 degree thing points to a possible clogged purge line. From the hollow bolt/nipple at the water crossover - next to the thermostat housing - over to the nipple on the side of the coolant surge tank. Remove the purge line from the (open) surge tank - hold the end in the tank neck and have an assistant start the engine normally. Steady stream of coolant ? If not, the line is plugged or the hollow bolt/nipple is. Rod out the bolt with coat hanger wire - 2.5 inches or so into the nipple. If the line is hopelessly clogged, replace it with a length of proper sized reinforced rubber fuel line from any parts store - new band clamps. Don't get carried away and break old plastic stuff.

Remove the water pump drive system belt cover and check the belt and tensioner pulley. That pulley should (must) be smooth and "viscous" when turned by hand. It may be replaced with a pulley from NAPA ($23) by simply removing the center bolt - no need to remove the entire tensioner arm if it's in good condition.
 

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White Diamond '03 DHS (with DTS floor shift)
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86 Bronco, 74 Ford LTD,1999 Deville, 1977 Coupe Deville
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I bought a deluxe test kit. But since my 99 Deville runs right at 196 degrees I have not used it.
I don't want to know what I don't want to know! Heh..Heh
 

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1998 Deville base
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Discussion Starter #16
Submariner409 said:
CO - Carbon monoxide, not 'dioxide'. If the tests were negative then you have some cooling system diagnosis to do.

In heavy or slow traffic with no A/C function set it's perfectly normal for these engines to warm to 224, fans go to SLOW, the engine cools to 213, the cycle repeats until you get back to open road and a bit of time at over 20 mph.

The 250 degree thing points to a possible clogged purge line. From the hollow bolt/nipple at the water crossover - next to the thermostat housing - over to the nipple on the side of the coolant surge tank. Remove the purge line from the (open) surge tank - hold the end in the tank neck and have an assistant start the engine normally. Steady stream of coolant ? If not, the line is plugged or the hollow bolt/nipple is. Rod out the bolt with coat hanger wire - 2.5 inches or so into the nipple. If the line is hopelessly clogged, replace it with a length of proper sized reinforced rubber fuel line from any parts store - new band clamps. Don't get carried away and break old plastic stuff.

Remove the water pump drive system belt cover and check the belt and tensioner pulley. That pulley should (must) be smooth and "viscous" when turned by hand. It may be replaced with a pulley from NAPA ($23) by simply removing the center bolt - no need to remove the entire tensioner arm if it's in good condition.
Purge line is clear. To be safe i already replaced it with a hose. The tube on the pump housing twists and turns a little bit, but i managed to push a large gauge wire over 4 inches. I get coolant flow anyway so.... Oh ive noticed that i can drive 10 miles on the highway to work in the morning with the temp barely getting past 197 maybe 199. And results r similar after work going 15 miles to my fiancé's house.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Anywhere from 188 to 205 is just fine for light traffic/open road running temperatures. IF the excessive system pressure (over 16 psi) occurs after 10 - 20 miles (complete warmup) and blows off coolant and the engine overheats, the pressure is coming from somewhere, and my money would be on exhaust gases in the cooling system.
 

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1998 Deville base
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Discussion Starter #18
Im now fairly certain my head gasket is no longer in the land of the living. I replaced the pump and lower hose last wednesday and flushed the system. I stuck the hose in the pump housing and didnt stop until clear water was rushing out of every hole i could see..... It behaved beautifully to and from work. It couldnt have been any more perfect. Then i took it up a hill about half a mile long and almost immediately started overheating. By the time i got to the top it was 255. Luckily my sisters house was nearby so i could let it sit and chill. Anybody know the best place to get remanufactured motors from?
 

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86 Bronco, 74 Ford LTD,1999 Deville, 1977 Coupe Deville
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If your engine runs fine , I would just have studs or inserts done to it. There's a few guy's around the country doing it as a specialty.
Where are you at? Some places are just a couple days in & out and your good to go.
NorthStar performance in Ontario is where I love to take mine. But i'm not overheating and it's a LOOOONG ways! Heh..Heh
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Yep - reman Northstars are a real crapshoot, and there are limits on which years and engine models (VIN 9, VIN Y) will interchange. (Your engine is a VIN Y - 275 hp, 3.11 economy final drive.)

Best to have a good local shop do a stud job - the bottom end is nearly bulletproof and extremely long-life. If no bad oil leaks or oil pressure problems, far better to do a (relatively) simple top overhaul along with timing chain tensioners and guide slippers.

Your 1998 should probably get new cam followers, too.

Please update your profile to show approximate location - it sure helps sometimes.
 
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